Field of the Invention
The invention relates to a heat exchanger, in particular an intercooler, comprising at least one header box that has a plate, wherein at least one tube approximately perpendicular to the plate engages a passage that projects out of the plate and surrounds a tube end, wherein the passage has a quasi-rectangular cross-section matched to the outer circumference of the tube.
Description of the Background Art
In order to achieve a performance improvement in an internal combustion engine, the air to be delivered for combustion can be compressed, for example with a turbocharger, before it is delivered to the combustion chambers of the internal combustion engine. However, the compression of the air simultaneously entails a significant heating of the same, which is disadvantageous for optimal functioning of the combustion process. For example, the heating may bring about premature ignition or increased nitrogen oxide emission. In order to avoid the adverse consequences of the overheated air delivered for combustion, a turbocharger is followed by a heat exchanger implemented as an intercooler, with which the compressed air is cooled to a permissible temperature prior to its combustion.
Known from DE 103 43 239 A1, which corresponds to US 2007/0000657, is a heat exchanger that has tubes and at least one header box, wherein the header box comprises at least one tube plate with passages, and the passages are bordered by side walls. In this way, the mechanical loading on the joint between the tube and plate is reduced without additional expenditure of material.
In the conventional art, in the case of reduced tube wall thicknesses or reduced plate thicknesses, the strength of the tube/plate joint is not always ensured, resulting in a reduced lifetime of an intercooler.
The stresses responsible for the failure of the intercooler arise here from non-uniform expansion of the individual components of the intercooler and the deformation or displacement resulting therefrom. The stresses can be attributed to the differing thermal conditions in the intercooler.
Known from DE 10 2007 059 673 A1 is a heat exchanger for exchanging between a first fluid and a second fluid, in which the service life of the heat exchanger with regard to cyclic thermal stress is extended by the means that a distance value, at least at a transition between the narrow side of the tube and the wide side of the tube is less than a distance value at the wide side of the tube in such a way that stresses in the region of the transition are reduced.
Another embodiment of passage geometry is known from DE 10 2007 016 528 A1, which corresponds to U.S. Pat. No. 7,413,006, where a header plate for use in a heat exchanger is disclosed. In order to improve loading of the tube/plate joint, the passage is formed such that it matches the outside of the associated tube.
However, a further reduced tube wall thickness below 0.5 mm or further reduced plate thicknesses below 3 mm result in fairly large deformations and displacements of the intercooler, especially in the tube/plate region. In this event, especially in the tube corner radii, the transition region between the relatively stiff passage and the thin tube, peak stresses arise that result in tearing between plate and tube. For this reason, the tube wall thickness and the plate thickness cannot be reduced further.